/*
 * jdmarker.c
 *
 * Copyright (C) 1991-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains routines to decode JPEG datastream markers.
 * Most of the complexity arises from our desire to support input
 * suspension: if not all of the data for a marker is available,
 * we must exit back to the application.  On resumption, we reprocess
 * the marker.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


typedef enum
{								/* JPEG marker codes */
	M_SOF0 = 0xc0,
	M_SOF1 = 0xc1,
	M_SOF2 = 0xc2,
	M_SOF3 = 0xc3,

	M_SOF5 = 0xc5,
	M_SOF6 = 0xc6,
	M_SOF7 = 0xc7,

	M_JPG = 0xc8,
	M_SOF9 = 0xc9,
	M_SOF10 = 0xca,
	M_SOF11 = 0xcb,

	M_SOF13 = 0xcd,
	M_SOF14 = 0xce,
	M_SOF15 = 0xcf,

	M_DHT = 0xc4,

	M_DAC = 0xcc,

	M_RST0 = 0xd0,
	M_RST1 = 0xd1,
	M_RST2 = 0xd2,
	M_RST3 = 0xd3,
	M_RST4 = 0xd4,
	M_RST5 = 0xd5,
	M_RST6 = 0xd6,
	M_RST7 = 0xd7,

	M_SOI = 0xd8,
	M_EOI = 0xd9,
	M_SOS = 0xda,
	M_DQT = 0xdb,
	M_DNL = 0xdc,
	M_DRI = 0xdd,
	M_DHP = 0xde,
	M_EXP = 0xdf,

	M_APP0 = 0xe0,
	M_APP1 = 0xe1,
	M_APP2 = 0xe2,
	M_APP3 = 0xe3,
	M_APP4 = 0xe4,
	M_APP5 = 0xe5,
	M_APP6 = 0xe6,
	M_APP7 = 0xe7,
	M_APP8 = 0xe8,
	M_APP9 = 0xe9,
	M_APP10 = 0xea,
	M_APP11 = 0xeb,
	M_APP12 = 0xec,
	M_APP13 = 0xed,
	M_APP14 = 0xee,
	M_APP15 = 0xef,

	M_JPG0 = 0xf0,
	M_JPG13 = 0xfd,
	M_COM = 0xfe,

	M_TEM = 0x01,

	M_ERROR = 0x100
} JPEG_MARKER;


/*
 * Macros for fetching data from the data source module.
 *
 * At all times, cinfo->src->next_input_byte and ->bytes_in_buffer reflect
 * the current restart point; we update them only when we have reached a
 * suitable place to restart if a suspension occurs.
 */

/* Declare and initialize local copies of input pointer/count */
#define INPUT_VARS(cinfo)  \
	struct jpeg_source_mgr * datasrc = (cinfo)->src;  \
	const JOCTET * next_input_byte = datasrc->next_input_byte;  \
	size_t bytes_in_buffer = datasrc->bytes_in_buffer

/* Unload the local copies --- do this only at a restart boundary */
#define INPUT_SYNC(cinfo)  \
	( datasrc->next_input_byte = next_input_byte,  \
	  datasrc->bytes_in_buffer = bytes_in_buffer )

/* Reload the local copies --- seldom used except in MAKE_BYTE_AVAIL */
#define INPUT_RELOAD(cinfo)  \
	( next_input_byte = datasrc->next_input_byte,  \
	  bytes_in_buffer = datasrc->bytes_in_buffer )

/* Internal macro for INPUT_BYTE and INPUT_2BYTES: make a byte available.
 * Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
 * but we must reload the local copies after a successful fill.
 */
#define MAKE_BYTE_AVAIL(cinfo,action)  \
	if (bytes_in_buffer == 0) {  \
	  if (! (*datasrc->fill_input_buffer) (cinfo))  \
	    { action; }  \
	  INPUT_RELOAD(cinfo);  \
	}  \
	bytes_in_buffer--

/* Read a byte into variable V.
 * If must suspend, take the specified action (typically "return FALSE").
 */
#define INPUT_BYTE(cinfo,V,action)  \
	MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
		  V = GETJOCTET(*next_input_byte++); )

/* As above, but read two bytes interpreted as an unsigned 16-bit integer.
 * V should be declared unsigned int or perhaps INT32.
 */
#define INPUT_2BYTES(cinfo,V,action)  \
	MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
		  V = ((unsigned int) GETJOCTET(*next_input_byte++)) << 8; \
		  MAKE_BYTE_AVAIL(cinfo,action); \
		  V += GETJOCTET(*next_input_byte++); )


/*
 * Routines to process JPEG markers.
 *
 * Entry condition: JPEG marker itself has been read and its code saved
 *   in cinfo->unread_marker; input restart point is just after the marker.
 *
 * Exit: if return TRUE, have read and processed any parameters, and have
 *   updated the restart point to point after the parameters.
 *   If return FALSE, was forced to suspend before reaching end of
 *   marker parameters; restart point has not been moved.  Same routine
 *   will be called again after application supplies more input data.
 *
 * This approach to suspension assumes that all of a marker's parameters can
 * fit into a single input bufferload.  This should hold for "normal"
 * markers.  Some COM/APPn markers might have large parameter segments,
 * but we use skip_input_data to get past those, and thereby put the problem
 * on the source manager's shoulders.
 *
 * Note that we don't bother to avoid duplicate trace messages if a
 * suspension occurs within marker parameters.  Other side effects
 * require more care.
 */


LOCAL           boolean get_soi(j_decompress_ptr cinfo)
/* Process an SOI marker */
{
	int             i;

	TRACEMS(cinfo, 1, JTRC_SOI);

	if(cinfo->marker->saw_SOI)
		ERREXIT(cinfo, JERR_SOI_DUPLICATE);

	/* Reset all parameters that are defined to be reset by SOI */

	for(i = 0; i < NUM_ARITH_TBLS; i++)
	{
		cinfo->arith_dc_L[i] = 0;
		cinfo->arith_dc_U[i] = 1;
		cinfo->arith_ac_K[i] = 5;
	}
	cinfo->restart_interval = 0;

	/* Set initial assumptions for colorspace etc */

	cinfo->jpeg_color_space = JCS_UNKNOWN;
	cinfo->CCIR601_sampling = FALSE;	/* Assume non-CCIR sampling??? */

	cinfo->saw_JFIF_marker = FALSE;
	cinfo->density_unit = 0;	/* set default JFIF APP0 values */
	cinfo->X_density = 1;
	cinfo->Y_density = 1;
	cinfo->saw_Adobe_marker = FALSE;
	cinfo->Adobe_transform = 0;

	cinfo->marker->saw_SOI = TRUE;

	return TRUE;
}


LOCAL           boolean get_sof(j_decompress_ptr cinfo, boolean is_prog, boolean is_arith)
/* Process a SOFn marker */
{
	INT32           length;
	int             c, ci;
	jpeg_component_info *compptr;

	INPUT_VARS(cinfo);

	cinfo->progressive_mode = is_prog;
	cinfo->arith_code = is_arith;

	INPUT_2BYTES(cinfo, length, return FALSE);

	INPUT_BYTE(cinfo, cinfo->data_precision, return FALSE);
	INPUT_2BYTES(cinfo, cinfo->image_height, return FALSE);
	INPUT_2BYTES(cinfo, cinfo->image_width, return FALSE);
	INPUT_BYTE(cinfo, cinfo->num_components, return FALSE);

	length -= 8;

	TRACEMS4(cinfo, 1, JTRC_SOF, cinfo->unread_marker, (int)cinfo->image_width, (int)cinfo->image_height, cinfo->num_components);

	if(cinfo->marker->saw_SOF)
		ERREXIT(cinfo, JERR_SOF_DUPLICATE);

	/* We don't support files in which the image height is initially specified */
	/* as 0 and is later redefined by DNL.  As long as we have to check that,  */
	/* might as well have a general sanity check. */
	if(cinfo->image_height <= 0 || cinfo->image_width <= 0 || cinfo->num_components <= 0)
		ERREXIT(cinfo, JERR_EMPTY_IMAGE);

	if(length != (cinfo->num_components * 3))
		ERREXIT(cinfo, JERR_BAD_LENGTH);

	if(cinfo->comp_info == NULL)	/* do only once, even if suspend */
		cinfo->comp_info = (jpeg_component_info *) (*cinfo->mem->alloc_small)
			((j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->num_components * SIZEOF(jpeg_component_info));

	for(ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
	{
		compptr->component_index = ci;
		INPUT_BYTE(cinfo, compptr->component_id, return FALSE);
		INPUT_BYTE(cinfo, c, return FALSE);
		compptr->h_samp_factor = (c >> 4) & 15;
		compptr->v_samp_factor = (c) & 15;
		INPUT_BYTE(cinfo, compptr->quant_tbl_no, return FALSE);

		TRACEMS4(cinfo, 1, JTRC_SOF_COMPONENT,
				 compptr->component_id, compptr->h_samp_factor, compptr->v_samp_factor, compptr->quant_tbl_no);
	}

	cinfo->marker->saw_SOF = TRUE;

	INPUT_SYNC(cinfo);
	return TRUE;
}


LOCAL           boolean get_sos(j_decompress_ptr cinfo)
/* Process a SOS marker */
{
	INT32           length;
	int             i, ci, n, c, cc;
	jpeg_component_info *compptr;

	INPUT_VARS(cinfo);

	if(!cinfo->marker->saw_SOF)
		ERREXIT(cinfo, JERR_SOS_NO_SOF);

	INPUT_2BYTES(cinfo, length, return FALSE);

	INPUT_BYTE(cinfo, n, return FALSE);	/* Number of components */

	if(length != (n * 2 + 6) || n < 1 || n > MAX_COMPS_IN_SCAN)
		ERREXIT(cinfo, JERR_BAD_LENGTH);

	TRACEMS1(cinfo, 1, JTRC_SOS, n);

	cinfo->comps_in_scan = n;

	/* Collect the component-spec parameters */

	for(i = 0; i < n; i++)
	{
		INPUT_BYTE(cinfo, cc, return FALSE);
		INPUT_BYTE(cinfo, c, return FALSE);

		for(ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
		{
			if(cc == compptr->component_id)
				goto id_found;
		}

		ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, cc);

	  id_found:

		cinfo->cur_comp_info[i] = compptr;
		compptr->dc_tbl_no = (c >> 4) & 15;
		compptr->ac_tbl_no = (c) & 15;

		TRACEMS3(cinfo, 1, JTRC_SOS_COMPONENT, cc, compptr->dc_tbl_no, compptr->ac_tbl_no);
	}

	/* Collect the additional scan parameters Ss, Se, Ah/Al. */
	INPUT_BYTE(cinfo, c, return FALSE);
	cinfo->Ss = c;
	INPUT_BYTE(cinfo, c, return FALSE);
	cinfo->Se = c;
	INPUT_BYTE(cinfo, c, return FALSE);
	cinfo->Ah = (c >> 4) & 15;
	cinfo->Al = (c) & 15;

	TRACEMS4(cinfo, 1, JTRC_SOS_PARAMS, cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);

	/* Prepare to scan data & restart markers */
	cinfo->marker->next_restart_num = 0;

	/* Count another SOS marker */
	cinfo->input_scan_number++;

	INPUT_SYNC(cinfo);
	return TRUE;
}


METHODDEF       boolean get_app0(j_decompress_ptr cinfo)
/* Process an APP0 marker */
{
#define JFIF_LEN 14
	INT32           length;
	UINT8           b[JFIF_LEN];
	int             buffp;

	INPUT_VARS(cinfo);

	INPUT_2BYTES(cinfo, length, return FALSE);
	length -= 2;

	/* See if a JFIF APP0 marker is present */

	if(length >= JFIF_LEN)
	{
		for(buffp = 0; buffp < JFIF_LEN; buffp++)
			INPUT_BYTE(cinfo, b[buffp], return FALSE);
		length -= JFIF_LEN;

		if(b[0] == 0x4A && b[1] == 0x46 && b[2] == 0x49 && b[3] == 0x46 && b[4] == 0)
		{
			/* Found JFIF APP0 marker: check version */
			/* Major version must be 1, anything else signals an incompatible change.
			 * We used to treat this as an error, but now it's a nonfatal warning,
			 * because some bozo at Hijaak couldn't read the spec.
			 * Minor version should be 0..2, but process anyway if newer.
			 */
			if(b[5] != 1)
				WARNMS2(cinfo, JWRN_JFIF_MAJOR, b[5], b[6]);
			else if(b[6] > 2)
				TRACEMS2(cinfo, 1, JTRC_JFIF_MINOR, b[5], b[6]);
			/* Save info */
			cinfo->saw_JFIF_marker = TRUE;
			cinfo->density_unit = b[7];
			cinfo->X_density = (b[8] << 8) + b[9];
			cinfo->Y_density = (b[10] << 8) + b[11];
			TRACEMS3(cinfo, 1, JTRC_JFIF, cinfo->X_density, cinfo->Y_density, cinfo->density_unit);
			if(b[12] | b[13])
				TRACEMS2(cinfo, 1, JTRC_JFIF_THUMBNAIL, b[12], b[13]);
			if(length != ((INT32) b[12] * (INT32) b[13] * (INT32) 3))
				TRACEMS1(cinfo, 1, JTRC_JFIF_BADTHUMBNAILSIZE, (int)length);
		}
		else
		{
			/* Start of APP0 does not match "JFIF" */
			TRACEMS1(cinfo, 1, JTRC_APP0, (int)length + JFIF_LEN);
		}
	}
	else
	{
		/* Too short to be JFIF marker */
		TRACEMS1(cinfo, 1, JTRC_APP0, (int)length);
	}

	INPUT_SYNC(cinfo);
	if(length > 0)				/* skip any remaining data -- could be lots */
		(*cinfo->src->skip_input_data) (cinfo, (long)length);

	return TRUE;
}


METHODDEF       boolean get_app14(j_decompress_ptr cinfo)
/* Process an APP14 marker */
{
#define ADOBE_LEN 12
	INT32           length;
	UINT8           b[ADOBE_LEN];
	int             buffp;
	unsigned int    version, flags0, flags1, transform;

	INPUT_VARS(cinfo);

	INPUT_2BYTES(cinfo, length, return FALSE);
	length -= 2;

	/* See if an Adobe APP14 marker is present */

	if(length >= ADOBE_LEN)
	{
		for(buffp = 0; buffp < ADOBE_LEN; buffp++)
			INPUT_BYTE(cinfo, b[buffp], return FALSE);
		length -= ADOBE_LEN;

		if(b[0] == 0x41 && b[1] == 0x64 && b[2] == 0x6F && b[3] == 0x62 && b[4] == 0x65)
		{
			/* Found Adobe APP14 marker */
			version = (b[5] << 8) + b[6];
			flags0 = (b[7] << 8) + b[8];
			flags1 = (b[9] << 8) + b[10];
			transform = b[11];
			TRACEMS4(cinfo, 1, JTRC_ADOBE, version, flags0, flags1, transform);
			cinfo->saw_Adobe_marker = TRUE;
			cinfo->Adobe_transform = (UINT8) transform;
		}
		else
		{
			/* Start of APP14 does not match "Adobe" */
			TRACEMS1(cinfo, 1, JTRC_APP14, (int)length + ADOBE_LEN);
		}
	}
	else
	{
		/* Too short to be Adobe marker */
		TRACEMS1(cinfo, 1, JTRC_APP14, (int)length);
	}

	INPUT_SYNC(cinfo);
	if(length > 0)				/* skip any remaining data -- could be lots */
		(*cinfo->src->skip_input_data) (cinfo, (long)length);

	return TRUE;
}


LOCAL           boolean get_dac(j_decompress_ptr cinfo)
/* Process a DAC marker */
{
	INT32           length;
	int             index, val;

	INPUT_VARS(cinfo);

	INPUT_2BYTES(cinfo, length, return FALSE);
	length -= 2;

	while(length > 0)
	{
		INPUT_BYTE(cinfo, index, return FALSE);
		INPUT_BYTE(cinfo, val, return FALSE);

		length -= 2;

		TRACEMS2(cinfo, 1, JTRC_DAC, index, val);

		if(index < 0 || index >= (2 * NUM_ARITH_TBLS))
			ERREXIT1(cinfo, JERR_DAC_INDEX, index);

		if(index >= NUM_ARITH_TBLS)
		{						/* define AC table */
			cinfo->arith_ac_K[index - NUM_ARITH_TBLS] = (UINT8) val;
		}
		else
		{						/* define DC table */
			cinfo->arith_dc_L[index] = (UINT8) (val & 0x0F);
			cinfo->arith_dc_U[index] = (UINT8) (val >> 4);
			if(cinfo->arith_dc_L[index] > cinfo->arith_dc_U[index])
				ERREXIT1(cinfo, JERR_DAC_VALUE, val);
		}
	}

	INPUT_SYNC(cinfo);
	return TRUE;
}


LOCAL           boolean get_dht(j_decompress_ptr cinfo)
/* Process a DHT marker */
{
	INT32           length;
	UINT8           bits[17];
	UINT8           huffval[256];
	int             i, index, count;
	JHUFF_TBL     **htblptr;

	INPUT_VARS(cinfo);

	INPUT_2BYTES(cinfo, length, return FALSE);
	length -= 2;

	while(length > 0)
	{
		INPUT_BYTE(cinfo, index, return FALSE);

		TRACEMS1(cinfo, 1, JTRC_DHT, index);

		bits[0] = 0;
		count = 0;
		for(i = 1; i <= 16; i++)
		{
			INPUT_BYTE(cinfo, bits[i], return FALSE);
			count += bits[i];
		}

		length -= 1 + 16;

		TRACEMS8(cinfo, 2, JTRC_HUFFBITS, bits[1], bits[2], bits[3], bits[4], bits[5], bits[6], bits[7], bits[8]);
		TRACEMS8(cinfo, 2, JTRC_HUFFBITS, bits[9], bits[10], bits[11], bits[12], bits[13], bits[14], bits[15], bits[16]);

		if(count > 256 || ((INT32) count) > length)
			ERREXIT(cinfo, JERR_DHT_COUNTS);

		for(i = 0; i < count; i++)
			INPUT_BYTE(cinfo, huffval[i], return FALSE);

		length -= count;

		if(index & 0x10)
		{						/* AC table definition */
			index -= 0x10;
			htblptr = &cinfo->ac_huff_tbl_ptrs[index];
		}
		else
		{						/* DC table definition */
			htblptr = &cinfo->dc_huff_tbl_ptrs[index];
		}

		if(index < 0 || index >= NUM_HUFF_TBLS)
			ERREXIT1(cinfo, JERR_DHT_INDEX, index);

		if(*htblptr == NULL)
			*htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);

		MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));
		MEMCOPY((*htblptr)->huffval, huffval, SIZEOF((*htblptr)->huffval));
	}

	INPUT_SYNC(cinfo);
	return TRUE;
}


LOCAL           boolean get_dqt(j_decompress_ptr cinfo)
/* Process a DQT marker */
{
	INT32           length;
	int             n, i, prec;
	unsigned int    tmp;
	JQUANT_TBL     *quant_ptr;

	INPUT_VARS(cinfo);

	INPUT_2BYTES(cinfo, length, return FALSE);
	length -= 2;

	while(length > 0)
	{
		INPUT_BYTE(cinfo, n, return FALSE);
		prec = n >> 4;
		n &= 0x0F;

		TRACEMS2(cinfo, 1, JTRC_DQT, n, prec);

		if(n >= NUM_QUANT_TBLS)
			ERREXIT1(cinfo, JERR_DQT_INDEX, n);

		if(cinfo->quant_tbl_ptrs[n] == NULL)
			cinfo->quant_tbl_ptrs[n] = jpeg_alloc_quant_table((j_common_ptr) cinfo);
		quant_ptr = cinfo->quant_tbl_ptrs[n];

		for(i = 0; i < DCTSIZE2; i++)
		{
			if(prec)
				INPUT_2BYTES(cinfo, tmp, return FALSE);
			else
				INPUT_BYTE(cinfo, tmp, return FALSE);
			quant_ptr->quantval[i] = (UINT16) tmp;
		}

		for(i = 0; i < DCTSIZE2; i += 8)
		{
			TRACEMS8(cinfo, 2, JTRC_QUANTVALS,
					 quant_ptr->quantval[i], quant_ptr->quantval[i + 1],
					 quant_ptr->quantval[i + 2], quant_ptr->quantval[i + 3],
					 quant_ptr->quantval[i + 4], quant_ptr->quantval[i + 5],
					 quant_ptr->quantval[i + 6], quant_ptr->quantval[i + 7]);
		}

		length -= DCTSIZE2 + 1;
		if(prec)
			length -= DCTSIZE2;
	}

	INPUT_SYNC(cinfo);
	return TRUE;
}


LOCAL           boolean get_dri(j_decompress_ptr cinfo)
/* Process a DRI marker */
{
	INT32           length;
	unsigned int    tmp;

	INPUT_VARS(cinfo);

	INPUT_2BYTES(cinfo, length, return FALSE);

	if(length != 4)
		ERREXIT(cinfo, JERR_BAD_LENGTH);

	INPUT_2BYTES(cinfo, tmp, return FALSE);

	TRACEMS1(cinfo, 1, JTRC_DRI, tmp);

	cinfo->restart_interval = tmp;

	INPUT_SYNC(cinfo);
	return TRUE;
}


METHODDEF       boolean skip_variable(j_decompress_ptr cinfo)
/* Skip over an unknown or uninteresting variable-length marker */
{
	INT32           length;

	INPUT_VARS(cinfo);

	INPUT_2BYTES(cinfo, length, return FALSE);

	TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker, (int)length);

	INPUT_SYNC(cinfo);			/* do before skip_input_data */
	(*cinfo->src->skip_input_data) (cinfo, (long)length - 2L);

	return TRUE;
}


/*
 * Find the next JPEG marker, save it in cinfo->unread_marker.
 * Returns FALSE if had to suspend before reaching a marker;
 * in that case cinfo->unread_marker is unchanged.
 *
 * Note that the result might not be a valid marker code,
 * but it will never be 0 or FF.
 */

LOCAL           boolean next_marker(j_decompress_ptr cinfo)
{
	int             c;

	INPUT_VARS(cinfo);

	for(;;)
	{
		INPUT_BYTE(cinfo, c, return FALSE);
		/* Skip any non-FF bytes.
		 * This may look a bit inefficient, but it will not occur in a valid file.
		 * We sync after each discarded byte so that a suspending data source
		 * can discard the byte from its buffer.
		 */
		while(c != 0xFF)
		{
			cinfo->marker->discarded_bytes++;
			INPUT_SYNC(cinfo);
			INPUT_BYTE(cinfo, c, return FALSE);
		}
		/* This loop swallows any duplicate FF bytes.  Extra FFs are legal as
		 * pad bytes, so don't count them in discarded_bytes.  We assume there
		 * will not be so many consecutive FF bytes as to overflow a suspending
		 * data source's input buffer.
		 */
		do
		{
			INPUT_BYTE(cinfo, c, return FALSE);
		} while(c == 0xFF);
		if(c != 0)
			break;				/* found a valid marker, exit loop */
		/* Reach here if we found a stuffed-zero data sequence (FF/00).
		 * Discard it and loop back to try again.
		 */
		cinfo->marker->discarded_bytes += 2;
		INPUT_SYNC(cinfo);
	}

	if(cinfo->marker->discarded_bytes != 0)
	{
		WARNMS2(cinfo, JWRN_EXTRANEOUS_DATA, cinfo->marker->discarded_bytes, c);
		cinfo->marker->discarded_bytes = 0;
	}

	cinfo->unread_marker = c;

	INPUT_SYNC(cinfo);
	return TRUE;
}


LOCAL           boolean first_marker(j_decompress_ptr cinfo)
/* Like next_marker, but used to obtain the initial SOI marker. */
/* For this marker, we do not allow preceding garbage or fill; otherwise,
 * we might well scan an entire input file before realizing it ain't JPEG.
 * If an application wants to process non-JFIF files, it must seek to the
 * SOI before calling the JPEG library.
 */
{
	int             c, c2;

	INPUT_VARS(cinfo);

	INPUT_BYTE(cinfo, c, return FALSE);
	INPUT_BYTE(cinfo, c2, return FALSE);
	if(c != 0xFF || c2 != (int)M_SOI)
		ERREXIT2(cinfo, JERR_NO_SOI, c, c2);

	cinfo->unread_marker = c2;

	INPUT_SYNC(cinfo);
	return TRUE;
}


/*
 * Read markers until SOS or EOI.
 *
 * Returns same codes as are defined for jpeg_consume_input:
 * JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
 */

METHODDEF int read_markers(j_decompress_ptr cinfo)
{
	/* Outer loop repeats once for each marker. */
	for(;;)
	{
		/* Collect the marker proper, unless we already did. */
		/* NB: first_marker() enforces the requirement that SOI appear first. */
		if(cinfo->unread_marker == 0)
		{
			if(!cinfo->marker->saw_SOI)
			{
				if(!first_marker(cinfo))
					return JPEG_SUSPENDED;
			}
			else
			{
				if(!next_marker(cinfo))
					return JPEG_SUSPENDED;
			}
		}
		/* At this point cinfo->unread_marker contains the marker code and the
		 * input point is just past the marker proper, but before any parameters.
		 * A suspension will cause us to return with this state still true.
		 */
		switch (cinfo->unread_marker)
		{
			case M_SOI:
				if(!get_soi(cinfo))
					return JPEG_SUSPENDED;
				break;

			case M_SOF0:		/* Baseline */
			case M_SOF1:		/* Extended sequential, Huffman */
				if(!get_sof(cinfo, FALSE, FALSE))
					return JPEG_SUSPENDED;
				break;

			case M_SOF2:		/* Progressive, Huffman */
				if(!get_sof(cinfo, TRUE, FALSE))
					return JPEG_SUSPENDED;
				break;

			case M_SOF9:		/* Extended sequential, arithmetic */
				if(!get_sof(cinfo, FALSE, TRUE))
					return JPEG_SUSPENDED;
				break;

			case M_SOF10:		/* Progressive, arithmetic */
				if(!get_sof(cinfo, TRUE, TRUE))
					return JPEG_SUSPENDED;
				break;

				/* Currently unsupported SOFn types */
			case M_SOF3:		/* Lossless, Huffman */
			case M_SOF5:		/* Differential sequential, Huffman */
			case M_SOF6:		/* Differential progressive, Huffman */
			case M_SOF7:		/* Differential lossless, Huffman */
			case M_JPG:		/* Reserved for JPEG extensions */
			case M_SOF11:		/* Lossless, arithmetic */
			case M_SOF13:		/* Differential sequential, arithmetic */
			case M_SOF14:		/* Differential progressive, arithmetic */
			case M_SOF15:		/* Differential lossless, arithmetic */
				ERREXIT1(cinfo, JERR_SOF_UNSUPPORTED, cinfo->unread_marker);
				break;

			case M_SOS:
				if(!get_sos(cinfo))
					return JPEG_SUSPENDED;
				cinfo->unread_marker = 0;	/* processed the marker */
				return JPEG_REACHED_SOS;

			case M_EOI:
				TRACEMS(cinfo, 1, JTRC_EOI);
				cinfo->unread_marker = 0;	/* processed the marker */
				return JPEG_REACHED_EOI;

			case M_DAC:
				if(!get_dac(cinfo))
					return JPEG_SUSPENDED;
				break;

			case M_DHT:
				if(!get_dht(cinfo))
					return JPEG_SUSPENDED;
				break;

			case M_DQT:
				if(!get_dqt(cinfo))
					return JPEG_SUSPENDED;
				break;

			case M_DRI:
				if(!get_dri(cinfo))
					return JPEG_SUSPENDED;
				break;

			case M_APP0:
			case M_APP1:
			case M_APP2:
			case M_APP3:
			case M_APP4:
			case M_APP5:
			case M_APP6:
			case M_APP7:
			case M_APP8:
			case M_APP9:
			case M_APP10:
			case M_APP11:
			case M_APP12:
			case M_APP13:
			case M_APP14:
			case M_APP15:
				if(!(*cinfo->marker->process_APPn[cinfo->unread_marker - (int)M_APP0]) (cinfo))
					return JPEG_SUSPENDED;
				break;

			case M_COM:
				if(!(*cinfo->marker->process_COM) (cinfo))
					return JPEG_SUSPENDED;
				break;

			case M_RST0:		/* these are all parameterless */
			case M_RST1:
			case M_RST2:
			case M_RST3:
			case M_RST4:
			case M_RST5:
			case M_RST6:
			case M_RST7:
			case M_TEM:
				TRACEMS1(cinfo, 1, JTRC_PARMLESS_MARKER, cinfo->unread_marker);
				break;

			case M_DNL:		/* Ignore DNL ... perhaps the wrong thing */
				if(!skip_variable(cinfo))
					return JPEG_SUSPENDED;
				break;

			default:			/* must be DHP, EXP, JPGn, or RESn */
				/* For now, we treat the reserved markers as fatal errors since they are
				 * likely to be used to signal incompatible JPEG Part 3 extensions.
				 * Once the JPEG 3 version-number marker is well defined, this code
				 * ought to change!
				 */
				ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
				break;
		}
		/* Successfully processed marker, so reset state variable */
		cinfo->unread_marker = 0;
	}							/* end loop */
}


/*
 * Read a restart marker, which is expected to appear next in the datastream;
 * if the marker is not there, take appropriate recovery action.
 * Returns FALSE if suspension is required.
 *
 * This is called by the entropy decoder after it has read an appropriate
 * number of MCUs.  cinfo->unread_marker may be nonzero if the entropy decoder
 * has already read a marker from the data source.  Under normal conditions
 * cinfo->unread_marker will be reset to 0 before returning; if not reset,
 * it holds a marker which the decoder will be unable to read past.
 */

METHODDEF       boolean read_restart_marker(j_decompress_ptr cinfo)
{
	/* Obtain a marker unless we already did. */
	/* Note that next_marker will complain if it skips any data. */
	if(cinfo->unread_marker == 0)
	{
		if(!next_marker(cinfo))
			return FALSE;
	}

	if(cinfo->unread_marker == ((int)M_RST0 + cinfo->marker->next_restart_num))
	{
		/* Normal case --- swallow the marker and let entropy decoder continue */
		TRACEMS1(cinfo, 2, JTRC_RST, cinfo->marker->next_restart_num);
		cinfo->unread_marker = 0;
	}
	else
	{
		/* Uh-oh, the restart markers have been messed up. */
		/* Let the data source manager determine how to resync. */
		if(!(*cinfo->src->resync_to_restart) (cinfo, cinfo->marker->next_restart_num))
			return FALSE;
	}

	/* Update next-restart state */
	cinfo->marker->next_restart_num = (cinfo->marker->next_restart_num + 1) & 7;

	return TRUE;
}


/*
 * This is the default resync_to_restart method for data source managers
 * to use if they don't have any better approach.  Some data source managers
 * may be able to back up, or may have additional knowledge about the data
 * which permits a more intelligent recovery strategy; such managers would
 * presumably supply their own resync method.
 *
 * read_restart_marker calls resync_to_restart if it finds a marker other than
 * the restart marker it was expecting.  (This code is *not* used unless
 * a nonzero restart interval has been declared.)  cinfo->unread_marker is
 * the marker code actually found (might be anything, except 0 or FF).
 * The desired restart marker number (0..7) is passed as a parameter.
 * This routine is supposed to apply whatever error recovery strategy seems
 * appropriate in order to position the input stream to the next data segment.
 * Note that cinfo->unread_marker is treated as a marker appearing before
 * the current data-source input point; usually it should be reset to zero
 * before returning.
 * Returns FALSE if suspension is required.
 *
 * This implementation is substantially constrained by wanting to treat the
 * input as a data stream; this means we can't back up.  Therefore, we have
 * only the following actions to work with:
 *   1. Simply discard the marker and let the entropy decoder resume at next
 *      byte of file.
 *   2. Read forward until we find another marker, discarding intervening
 *      data.  (In theory we could look ahead within the current bufferload,
 *      without having to discard data if we don't find the desired marker.
 *      This idea is not implemented here, in part because it makes behavior
 *      dependent on buffer size and chance buffer-boundary positions.)
 *   3. Leave the marker unread (by failing to zero cinfo->unread_marker).
 *      This will cause the entropy decoder to process an empty data segment,
 *      inserting dummy zeroes, and then we will reprocess the marker.
 *
 * #2 is appropriate if we think the desired marker lies ahead, while #3 is
 * appropriate if the found marker is a future restart marker (indicating
 * that we have missed the desired restart marker, probably because it got
 * corrupted).
 * We apply #2 or #3 if the found marker is a restart marker no more than
 * two counts behind or ahead of the expected one.  We also apply #2 if the
 * found marker is not a legal JPEG marker code (it's certainly bogus data).
 * If the found marker is a restart marker more than 2 counts away, we do #1
 * (too much risk that the marker is erroneous; with luck we will be able to
 * resync at some future point).
 * For any valid non-restart JPEG marker, we apply #3.  This keeps us from
 * overrunning the end of a scan.  An implementation limited to single-scan
 * files might find it better to apply #2 for markers other than EOI, since
 * any other marker would have to be bogus data in that case.
 */

GLOBAL          boolean jpeg_resync_to_restart(j_decompress_ptr cinfo, int desired)
{
	int             marker = cinfo->unread_marker;
	int             action = 1;

	/* Always put up a warning. */
	WARNMS2(cinfo, JWRN_MUST_RESYNC, marker, desired);

	/* Outer loop handles repeated decision after scanning forward. */
	for(;;)
	{
		if(marker < (int)M_SOF0)
			action = 2;			/* invalid marker */
		else if(marker < (int)M_RST0 || marker > (int)M_RST7)
			action = 3;			/* valid non-restart marker */
		else
		{
			if(marker == ((int)M_RST0 + ((desired + 1) & 7)) || marker == ((int)M_RST0 + ((desired + 2) & 7)))
				action = 3;		/* one of the next two expected restarts */
			else if(marker == ((int)M_RST0 + ((desired - 1) & 7)) || marker == ((int)M_RST0 + ((desired - 2) & 7)))
				action = 2;		/* a prior restart, so advance */
			else
				action = 1;		/* desired restart or too far away */
		}
		TRACEMS2(cinfo, 4, JTRC_RECOVERY_ACTION, marker, action);
		switch (action)
		{
			case 1:
				/* Discard marker and let entropy decoder resume processing. */
				cinfo->unread_marker = 0;
				return TRUE;
			case 2:
				/* Scan to the next marker, and repeat the decision loop. */
				if(!next_marker(cinfo))
					return FALSE;
				marker = cinfo->unread_marker;
				break;
			case 3:
				/* Return without advancing past this marker. */
				/* Entropy decoder will be forced to process an empty segment. */
				return TRUE;
		}
	}							/* end loop */
}


/*
 * Reset marker processing state to begin a fresh datastream.
 */

METHODDEF void reset_marker_reader(j_decompress_ptr cinfo)
{
	cinfo->comp_info = NULL;	/* until allocated by get_sof */
	cinfo->input_scan_number = 0;	/* no SOS seen yet */
	cinfo->unread_marker = 0;	/* no pending marker */
	cinfo->marker->saw_SOI = FALSE;	/* set internal state too */
	cinfo->marker->saw_SOF = FALSE;
	cinfo->marker->discarded_bytes = 0;
}


/*
 * Initialize the marker reader module.
 * This is called only once, when the decompression object is created.
 */

GLOBAL void jinit_marker_reader(j_decompress_ptr cinfo)
{
	int             i;

	/* Create subobject in permanent pool */
	cinfo->marker = (struct jpeg_marker_reader *)
		(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, SIZEOF(struct jpeg_marker_reader));
	/* Initialize method pointers */
	cinfo->marker->reset_marker_reader = reset_marker_reader;
	cinfo->marker->read_markers = read_markers;
	cinfo->marker->read_restart_marker = read_restart_marker;
	cinfo->marker->process_COM = skip_variable;
	for(i = 0; i < 16; i++)
		cinfo->marker->process_APPn[i] = skip_variable;
	cinfo->marker->process_APPn[0] = get_app0;
	cinfo->marker->process_APPn[14] = get_app14;
	/* Reset marker processing state */
	reset_marker_reader(cinfo);
}
